The present invention relates in general to key locks, and more particularly to key locks for safe deposit boxes and the like, wherein both a guard key or "prep" key and a renter's key having a proper configuration on the key bit must be inserted into the lock and rotated to effect retraction of the bolt, and wherein the lock is capable of being changed in the field for different guard or prep keys and for different renter keys.
It will be appreciated that safe deposit boxes in bank vaults and similar security installations are successively leased to different parties, to whom the lessor furnishes a renter's key adapted to open a given safe deposit box when the lock is partially operated or armed by a guard or prep key in the possession of the lessor. Often, lessees fail to return the renter's key at the expiration of their lease, or the lessee may lose the renter's key, and it becomes necessary in such cases to change the safe deposit key lock so that it can be operated by a renter's key bit having a different configuration. Also, even if the lessee returns the renter's key at the expiration of his lease, it is desirable to change the key bit configuration to which the lock is responsive whenever the lessee of the box is changed, to prevent the otherwise possible use of an unauthorized duplicate of the renter's key which may have been made before the renter's key was returned.
For this reason, certain safe deposit locks have been made in such a manner that the position of the gatings in the tumblers operated by the renter's key is changeable, so that the position of the gatings may be adjustably set to be opened by a different renter's key. The typical practice in this regard has been to provide a change key in the form of a non-round cross-section rod which is insertable into an opening in the safe deposit lock case or rear cover wall and through shaped openings in the renter's key tumblers, when the safe deposit lock has been activated by the old renter's key. The combination change key interfits into shaped openings in one of two pivoted companion tumbler sectors for each of the renter's key tumbler levers, all of which tumbler lever sectors are pivoted on a fixed tumbler post, to decouple the normally mated tumbler lever sections of each of these tumbler levers and permit them to be recoupled in a position corresponding to the configuration of the bit of a new renter's key.
It has become recognized that it is also desirable to provide for the setting of the guard key or prep key tumbler lever system in accordance with different guard key or prep key configurations (hereinafter generally referred to as the prep key), so that the prep key to be used with safe deposit locks can be changed from time to time to provide greater security or to reset the locks when the prep key is lost or when change of guard personnel occurs. Attempts to provide for changing the lock to accommodate different prep keys as well as different renter keys have generally involved use of renter's key tumbler levers which are either made up of two pivoted companion tumbler sectors which may be selectively decoupled when the lock is in a change mode to permit relative adjustment of one of the tumbler sectors with respect to the other to accommodate the configuration of the bit of the new renter's key, and also using an entirely different set of prep key tumbler levers disposed in a portion of the lock housing spaced from the renter's key tumbler levers and a plurality of independently adjustable fence members positioned relative to the prep key tumblers capable of being set to different positions in accordance with different guard key configurations. Such a construction requires a considerably larger space-consuming lock configuration and considerably increases complications and expense in the assembly of safe deposit lock units.
The present invention is directed to a double changeable safe deposit box key lock having a single set of tumbler levers operated by both a guard key and a renter key and coactive with a set of a number of slidable fences corresponding to the number of tumbler levers, as distinguished from many prior safe deposit box locks of the tumbler lever types which employ two sets of tumbler levers, one set for operation by the guard key and another set for operation by the renter key. The single lever function is worked by both the guard key and the renter key, the guard key setting the pivot point of the tumbler levers, and the renter key setting the slidable fences when the lock is in a change condition. A change screw is loosened at the change condition to enable the slidable fences to move in response to the key bitting on the renter key, and after setting of the position of the slidable fences by setting of the tumbler lever positions responsive to a renter key, the change screw is tightened to hold the fences in the position to which they are set by the levers and bitting on the new renter key and also responsive to the guard key setting of the pivot points of the levers.
An object of the present invention is the provision of a novel construction of a tumbler lever lock for safe deposit boxes and the like, having a single set of tumbler levers and a single set of a corresponding number of slidable fences, wherein the pivot points of the tumbler levers are set by a guard key and the tumblers levers are properly positioned by the bitting on the renter key so as to align gate recesses and edges of the tumbler levers confronting fence formations on the slidslidable fences to enable movement of the lock to unlocking position. Simplification is achieved by enabling both renter key change and guard key change of the tumbler lever positions by one change screw associated with the set of slidable fences, and either both the renter key and the guard key or one of the renter or guard keys can be changed as desired by use of the single change screw.
Other objects, advantages and capabilities of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention.